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Monday, 25 July 2011

Making Peace with Tomato Horn Worms

When I first started growing tomatoes I used to pick off the tomato or tobacco hornworms and squish them with a rock. Then one year I missed one and spotted it with the tiny white eggs from a parasitic wasp on it's back. Ever since then I've made peace with the hornworms in my garden. I never pick them off or do anything to get rid of them. They get to eat some tomatoes leaves and a tomato here and there in complete peace. Why the change of heart? I don't want to get rid of them and risk the parasitic wasp not having a host for it's eggs. I also don't want the birds to go hungry, as they seem to find these giant juicy worms a complete breakfast. The truth is they're not that damaging to tomato plants and I can plant extra plants just for them. Perhaps a little defoliation is good for tomatoes this time of year and I don't mind losing a couple tomatoes, I have plenty to go around. The truth is that often when we step in we upset the balance of nature and make our problems worse down the line. If we squish or kill all the hornworms we'll never have the braconid wasps in our gardens. Without the wasps we'll end up with more hornworms, aphids and other insects. We may also inadvertently kill a hornworm that has already been parasitized by a wasp since it takes a few days before the white worms appear on their backs. I'm convinced that I'm encouraging biodiversity in my garden by making peace with hornworms and other things viewed as "pests". I have noticed that the less I interfere with nature the more balanced things become, even in my small quarter acre garden. I encourage you to let the hornworms and other pests live and see how everything balances out in a few years!

Do you have any pests that you've made peace with?

Here's an interesting article from the BBC about how plants can send out SOS signals to predatory insects when they sense they're being attacked by caterpillars & other insects. And the specifically studies hornworms.

14 comments:

Great post. One of the reasons organically grown plants are more nutritious is that they have to defend themselves against herbivores. The chemicals plants produce to defend themselves are often the very antioxidants etc. that make them good for us to eat. Some plants even communicate with their neighbors - bug eats part of one plant, that plant produces compounds its neighbors can sense, all its neighbors crank up their antioxidant production. So who knows, maybe all your tomatoes are more nutritious when one of the plants get damaged.

One of the things I love about reading other people's blogs is that it seems someone gives me something to learn, or a new slant on things that I have never considered before.

You did that for me today. I saw one of these worms on one of my tomato plants this summer. I didn't do anything about it because that tomato plant was already so damaged by the heat and the drought we're having that I just said, "Go for it", and went on.

I try to grow organically as much as possible. When I've had fruit trees, I usually just do a dormant spray of Volck oil. I have found that when the tree goes into production, the first fruits to ripen are wormy. If I can salvage any of them, they are what I make jam out of, or they go to the compost pile. Seems the fruits that ripen after those first ones are then bigger and hardly ever infested. I hesitate to get into massive spraying of chemicals on my fruit trees because I've heard stories of people who died of cancer after years of doing so. Maybe it was the chemicals they sprayed. Maybe it was the fruit they ate. Or maybe something else, but the less chances you take, the better.

Another reason to leave them alone is that they pupate into the Hawk Moth aka Humingbird Moth, which is a pollinator of some plants. According to one book I read, they were dependent on the papaw tree and as humans cut so many of these trees down, they moved over to the tomato and pepper plants to survive.

I agree with Linda Z there. My chickens and ducks love hornworms, so I'd always handpick the caterpillars and toss them into their pens. But since I found out the hornworms turn into hummingbird moths, and those are so cool, I've let the hornworms be. I might only get 3-4 all summer long, so they're not that big a problem for the beauty they become.

Live and let live! I know.....The thing is, Tomato horn worms are pest, that aren't that pesky.... I grow quite allot of tomatoes, but rarely see more than a few thw. Besides they pollinate my apple cactus when they grow up.

That being said, there are bugs that are much less cool looking and helpful than thw, just way more destructive....I'm proud to say that I do not use pesticides! None. I pay though. I'm beaten to the ground in the years where I lose 90% of my plum crop, or 100% of my squash(as is on track for this year! very discouraging). Balance is a great concept, its just that the pest that are pesky, have an upper hand............

When I rented an apartment with a walled garden I had to make peace with the wasps. They were eating all my grapes, didn't want to leave when I tried "granny knows best" solutions... Well, at the end I did not really make peace with them, I had to surrender, there were probably at least 50 of them in my 2 square meters. My sister got really scared of all those wasps if she visited me!

I have a conservation biologist/ entomologist friend who told me about the endangered hornworm in Hawaii, and said enjoy the hornworms we have here (Calif) while they're still here. 'Cause people see and kill them all the time, so apparently their population is in decline (I assume much larger impacts are from pesticides/habitat loss).

So, now I keep them. =) And, you're right, they don't eat all that much, and opening up the canopy probably helps with air circulation, etc. (total guess, but...)

As John Muir said (in so many words), it exists and is valuable for its own sake. =)